The problem is coming from the material, I think. Something to do with world location.
But if you only have a few trees ( < 1200 ) I wouldn’t bother, just plonk them in the level. You aren’t going to see any real difference in draw calls.
If you have a large number and want to cut down on draw calls then use the foliage tool. That’s what it’s for. Do the whole lot with 1 draw call… 